The message I took away from this chapter was that, for an animal to have a big brain in adulthood, it must have a large brain at birth. During our evolution, human beings have evolved in such a way so as allow for offspring to have a huge brain at birth - even though an adult mountain gorilla may ultimately weigh in at 200kg, a human baby is almost twice the size of that same gorilla at birth!
One question that I had was "why is birth brain size so important?" That is, why can't the brain of an animal grow massively after birth thereby allowing for a safer and easier birthing process? I did not see an answer to this in the chapter.
Another point from this chapter was that, according to the authors, the mosaic theory of brain development does not find support in studies that compare the sizes of brains amongst primates. Specifically, mosaic predicts that brain areas that are more useful should be larger than others. But instead the brain regions appear to be the same relative sizes in all primates. Useful brain regions are larger in humans, from an absolute standpoint, because the human brain is larger.
In an interview with Dr. Ginger Campbell on the Brain Science Podcast, Dr. Lynch mentions that a nice aspect to this theory is that it does not require special explanations regarding how evolution selected for intelligence, it just requires that evolution select for large brains. While part of this can be explained by simply increasing the size of a human being (chimps and gorillas need larger brains than monkeys because their bodies are larger), this does not entirely explain human beings, because we have large brains even when compared to other primates.
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